Beta-2 adrenergic receptor (ADRB2) (ADRB2)

The Beta-2 adrenergic receptor (ADRB2) is a G protein-coupled receptor (GPCR) that serves as the primary regulator of airway smooth muscle tone in the human respiratory system [1, 2]. Expressed predominantly on bronchial smooth muscle cells, its activation triggers the Gs-adenylyl cyclase-cAMP signaling pathway, which promotes muscle relaxation and subsequent bronchodilation [3, 4]. This receptor is the central therapeutic target for managing obstructive airway diseases, including asthma and chronic obstructive pulmonary disease (COPD) [1, 12]. Pharmacological agents targeting ADRB2 include short-acting beta-agonists (SABAs) for rapid symptom relief and long-acting beta-agonists (LABAs) for long-term maintenance [2, 9]. Endogenous catecholamines like epinephrine naturally activate this system to maintain airway patency during physiological stress [2]. Despite its high therapeutic index, chronic stimulation can lead to receptor desensitization and downregulation, potentially diminishing drug efficacy over time [5, 8]. Furthermore, systemic absorption or high doses may cause off-target effects such as tachycardia and tremors, necessitating careful dosing and often combination therapy with inhaled corticosteroids to address underlying inflammation [7, 11]. The receptor's function is also influenced by genetic polymorphisms, which can affect individual responses to bronchodilator therapy [14].

Other names

Beta-2 adrenoceptorB2ARADRB2RAdrenoceptor beta 2Beta-2 adrenoreceptor

Agonist binding to the Beta-2 adrenergic receptor activates the stimulatory G protein (Gs), which stimulates adenylyl cyclase to produce cyclic adenosine monophosphate (cAMP). Increased cAMP levels activate protein kinase A (PKA), leading to the phosphorylation of target proteins that sequester intracellular calcium and inhibit myosin light-chain kinase, ultimately resulting in airway smooth muscle relaxation and bronchodilation [1, 2, 4].